Vehicle theft continues to increase in society today with added expense to consumers in insurance cost, time loss and inconvenience. Consumers are looking for vehicles that are more secure from theft. Insurance companies are offering premium discounts for vehicles equipped with different types of vehicle anti-theft devices, such as steering wheel locking devices, alarm systems, and ignition switches which use electronically controlled keys, etc.
There are many different types of vehicle anti-theft devices to deter thieves. Some are intended to audibly alert the owner of a vehicle that their vehicle is being tampered with, and are of the alarm or noise making type. Some inventions are anti-theft devices which lock the vehicle steering system in an attempt to prevent theft. Other anti-theft devices close off the fuel supply to prevent theft. If a vehicle equipped with such a device were stolen, it could be driven only a few blocks before running out of the remaining fuel in its fuel line.
Some inventions are used in conjunction with the vehicle hydraulic brake system to prevent theft. The following are a few examples: U.S. Pat No. 4,873,824 issued to Cox explains an anti-theft brake locking mechanism placed between the master cylinder and the brake actuator, that can be operated from the driver area, by key or combination mechanism. The mechanism can lock mechanically or electronically. Although this device appears to fulfill the function of locking the brakes, it appears to lack the ability to lock the brakes if the brakes are out of adjustment. Also, it would entail elimination of the brake light pressure switch with added cost of a mechanical switch added to the system. If the pressure switch were not eliminated, the brake lights would remain on while the mechanism was operational, thus discharging the battery.
U.S. Pat No. 4,951,776 issued to Jetter explains an anti-theft system that includes an actuating means to temporarily disable a vehicle from theft. This invention assembly has a solenoid valve which is installed in the hydraulic brake system. When the solenoid is energized, the valve is open and the brake system operates in a normal manner. When the assembly is de-energized, the valve closes and prevents the release of the brakes. This invention appears to have the ability to lock the brakes, except that it has a self-equalizing drawback. This drawback allows the brake pressure trapped between the brake drum (or rotor) and the invention to dissipate in approximately one hour, thereby allowing the brakes to release. This defeats the anti-theft function.
U.S. Pat No. 5,351,781 issued to Pritchard et al., explains an anti-theft device consisting of a housing unit located between the master cylinder and proportioning valve. The housing unit has a fluid blocking means to block and unblock the flow of brake fluid. It is controlled by a 12 volt DC motor which is actuated between limit switches to open and close the valve. Although this invention attempts to fulfill its intended purpose, the problem of having many mechanical and electrical moving parts could lead to premature failure. Additionally, this factor increases manufacturing costs.